I'm happy enough with where I've got all the mechs for now so on to the other half, Briggs and Stratton model 91202 0059 01 , made in July 1992.
First up are to drain the oil, which looks like treacle and fix the stuck throttle on the handlebars. I spent ages trying to find the manual, but the model on the 91202 manual looks nothing like mine. The oil drain looked like a square key rather than a bolt. I spent ages trying to find one, and it turns out it is actually a hex key, just had grease in it that made it look square. So the oil is draining overnight, and I've taken the the throttle cable off and lubed it then hung it for the night so hopefully some lube will work it's way down inside the casing.
Picked up a new air filter, still available after 30 years, new plug and had oil, so tomorrow will get it all in and see if it starts..
